Transport of magnetoexcitons in single and coupled quantum wells

TL;DR

This paper investigates how magnetoexcitons move in single and coupled quantum wells, analyzing their relaxation times and mean free paths under various scattering conditions and magnetic fields.

Contribution

It provides a detailed calculation of magnetoexciton transport properties considering different types of disorder and magnetic field effects, highlighting nonmonotonous behaviors.

Findings

Transport relaxation time depends nonmonotonously on magnetic momentum in certain scattering cases.

Mean free path exhibits maxima at non-zero magnetic momentum, influenced by well separation and disorder.

Maximum mean free path varies with magnetic field strength and scattering type.

Abstract

The transport relaxation time $\tau (P)$ and the mean free path of magnetoexcitons in single and coupled quantum wells are calculated ($P$ is the magnetic momentum of the magnetoexciton). We present the results for magnetoexciton scattering in a random field due to (i) quantum well width fluctuations, (ii) composite fluctuations and (iii) ionized impurities. The time $\tau(P)$ depends nonmonotonously on $P$ in the case (ii) and in the cases (i), (iii) for $D/l$ smaller than some critical value ($D$ is the interwell separation, $l=\sqrt{\hbar c/eH}$ is the magnetic length). For $D/l\gg 1$ the transport relaxation time increases monotonously with $P$. The magnetoexciton mean free path $\lambda (P)$ has a maximum at $P\ne 0$ in the cases (i), (iii). It decreases with increasing $D/l$. The mean free path calculated for the case (ii) may have two maxima. One of them disappears with the variation of the random fields parameters. The maximum of $\lambda (P)$ increases with $H$ for types (i,iii) of scattering processes and decreases in the case (ii).